In recent years, plural telecommunications standards called third generation are adopted as IMT-2000 by the International Telecommunications Union (ITU) for high-speed CDMA mobile telecommunications methods. For W-CDMA (FDD: Frequency Division Duplex) which is one of the plural telecommunications standards, commercial services were started in Japan in 2001. For W-CDMA systems, the standardization organization 3GPP (3rd Generation Partnership Project) determined the first specifications to summarize them as the release 1999th edition (Version name: 3.x.x) in 1999. Currently, release 4 and release 5 are specified as other new versions of the release 1999th edition, and release 6 is under review and being created.
Hereafter, related main channels will be explained below briefly. As physical-layer channels which are individually assigned to a mobile station as release-1999-compliant channels, there are a DPCCH (Dedicated Physical Control CHannel) and a DPDCH (Dedicated Physical Data CHannel). The DPCCH is a channel via which various pieces of control information for a physical layer (e.g., a pilot signal for synchronization and a transmission-power-control signal) are transmitted. The DPDCH is a channel via which various data from a MAC layer (Media Access Control: a protocol layer which is located above the physical layer) are transmitted. Incidentally, channels used for transmission of data between the MAC layer and the physical layer is called transport channels (Transport channels). In release 1999, a transport channel which corresponds to the DPDCH which is the physical-layer channel is called a DCH (Dedicated Channel). The above-mentioned DPCCH and DPDCH are set up for both uplink and downlink.
In release 5, an HSDPA (High Speed Downlink Packet Access) technology is introduced in order to achieve increase in the efficiency of the packet transmission via downlinks, and, as physical-layer channels for downlinks, an HS-PDSCH (High Speed-Physical Downlink Shared CHannel) and an HS-SCCH (High Speed-Shared Control CHannel) are added. The HS-PDSCH and the HS-SCCH are used by two or more mobile stations. The HS-PDSCH is a channel via which data from the MAC layer are transmitted, like the release-1999-compliant DPDCH. The HS-SCCH is a channel via which control information (e.g., a modulation method of transmission data and a packet data size) at the time of transmitting data via the HS-PDSCH is transmitted.
The spreading factor of the HS-PDSCH is fixed to 16, and two or more spread codes (i.e., two or more channels) can be assigned to one mobile station at a time of packet transmission. Allocation control (what is called scheduling) is carried out by a base station (i.e., a fixed station). In release 5, an HS-DPCCH (High Speed-Dedicated Physical Control CHannel) is added as a physical-layer channel for uplinks. The mobile station transmits a reception judgment result (ACK/NACK) for data sent thereto via the HS-PDSCH, and downlink radio environment information (CQI: Channel Quality Information) to the base station using the HS-DPCCH.
The base station transmits HS-PDSCH and HS-SCCH data in a pair. The mobile station receives the HS-PDSCH and HS-SCCH data which are sent from the base station, judges whether the data include any error, and transmits a judgment result (ACK/NACK) using the HS-DPCCH. Therefore, the frequency with which the mobile station transmits ACK/NACK to the base station varies according to the frequency of the downlink packet transmission. The mobile station also transmits CQI to the base station according to the value of a period which is set up in advance of the communications.
When transmitting data using the DPDCH, the transmit side piggybacks information about a multiplexing method of multiplexing the data and the size of data per unit time (i.e., a transmission rate), which are transmitted from the higher-level protocol layer, onto the DPCCH, and transmits the information to the receive side to notify it to the receive side. The notification information containing “the multiplexing method of multiplexing data” and “the data size” is called TFC (Transport Format Combination), and TFCI (TFC Index) which is the index of TFC is transmitted to the receive side. When the transmission rate is decided by TFC, a gain factor (βd) which defines the transmit power of the DPDCH is decided. The whole of TFC which can be provided when transmission is called TFCS (TFC Set), and is setup between the mobile station and the fixed station at the time of initial settings for communications or during communications. Furthermore, for each TFC, a transition among states (support, Excess Power, and Block) is defined, and that the state (and state transition) of each TFC is determined so that it reflects the state of the transmission is defined in the written standards TS25.321 (see Chapter 11.4 of nonpatent reference 1, and FIG. 11.4.1 of Transport format combination selection in UE). A transition among the states of each TFC for the DPDCH is made to take place by evaluating (Evaluation) the number of unit transmission times (slot: 1/15 of 10 milliseconds) that the total transmit power value (an estimated or actual measurement) of the mobile station reaches a maximum transmit power predetermined value (or a maximum transmit power set value). This is defined by the technical specification TS25.133 (see Chapter 6.4 of nonpatent reference 2, and Chapter 6.4.2 Requirements of Transport format combination selection in UE).    [Patent reference 1] JP,2004 2115276,A JP,2004-215276 A    [Nonpatent reference 1] 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Medium Access Control (MAC) protocol specification (Release 5) 3GPP TS 25.321 V5.9.0 (2004-06)    [Nonpatent reference 2] 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Requirements for support of radio resource management (FDD) (Release 5) 3GPP TS 25.133 V5.12.0 (2004-09)    [Nonpatent reference 3] 3rd Generation Partnership Project Technical Specification Group Radio Access Network; Feasibility Study for Enhanced Uplink for UTRA FDD (Release 6) 3GPP TS 25.309 V6.1.0 (2004-12)    [Nonpatent reference 4] 3GPP TSG RAN WG2 Meeting #45 Shin-Yokohama, Japan, 15-19 Nov., 2004 Tdoc R2-042447 Agenda Item: 12.2 Title: Consideration on E-TFC selection principles    [Nonpatent reference 5] 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; User Equipment (UE) radio transmission and reception (FDD) (Release 5) 3GPP TS 25.101 V5.12.0 (2004-09)
Release 1999 is decided by mainly assuming transmission and reception of continuous data like voice calls. In release 5, HSDPA which makes it possible to carry out downlink high-speed packet communications is added, though no specifications assuming uplink high-speed packet communications are not developed but the release 1999 specifications are applied just as they are. Therefore, also in a case in which burst (Burst) transmission like transmission of packet data from a mobile station to a base station is carried out, dedicated channels (DCH and DPDCH) for exclusive use must be assigned to each mobile station. Therefore, by taking into consideration an increase in demand of uplink packet data transmission which is caused by the widespread use of the Internet, there is a problem from the viewpoint of the effective use of the radio resources.
Data transmission from a mobile station is performed through autonomous transmission control (Autonomous Transmission) by the mobile station. In this case, the transmission timing from each mobile station is defined arbitrarily (or at a statistically random) The system in which the mobile station is carrying out the autonomous transmission control and the data transmission, the fixed station is not concerned about the transmission timing of the mobile station. In a communication system to which the CDMA communications method is applied, although transmission from other mobile stations all serves as a source of interference, a fixed station which manages the radio resources can only carry out a statistical prediction (or management) of the amount of interference noises and an amount of variations in the amount of interference noises for the base station's reception. Thus, because the fixed station which manages the radio resources in the communications system using the CDMA communication method is not concerned about the transmission timing of each mobile station and cannot predict correctly the amount of interference noises, the fixed station carries out radio resource allocation control which ensures a sufficient margin by assuming a case in which the amount of variations in the interference noise amount is large. Such radio resource management by a fixed station is carried out by not a base station itself, but a base station control apparatus (RNC: Radio Network Controller) which adjusts two or more base stations.
The radio resource management which the base station control apparatus (RNC) carries out for mobile stations and notifications which accompany the radio resource management need a relatively-long processing time (of the order of several 100 milliseconds). For this reason, no appropriate control of the allocation of the radio resources according to a rapid change in the radio transmission environment, the transmission states of other mobile stations (=the amount of interference from other mobile stations), etc. cannot be carried out. Therefore, in release 6, an introduction of an E-DCH (Enhanced DCH) technology is examined in order to implement the effective use of the radio resources and high-speed allocation of the radio resources. The E-DCH technology may be called HSUPA (High Speed Uplink Packet Access). In the E-DCH technology, not only an AMC (Adaptive Modulation and Coding) technology, an HARQ (Hybrid Automatic Repeat reQuest) technology, etc. which are introduced for HSDPA in release 5, but also a short transmission time interval (TTI: Transmission Time Interval) can be used. The E-DCH means a transport channel which is an extension of a DCH which is a transport channel which complies with the conventional standards, and is set up independently of the DCH.
For the E-DCH, the fixed station carries out uplink radio resource control which is called “scheduling.” Because the electric wave propagation environment and so on differ between uplinks and downlinks, the scheduling differs from the scheduling for the HSDPA. The mobile station carries out control of transmission of data on the basis of scheduling results notified from the fixed station. The fixed station transmits a judgment result (ACK/NACK) for the received data to the mobile station. A base station (referred to as NodeB in 3GPP) is assumed as an apparatus which is included in fixed stations and which carries out the scheduling. An example of a concrete method of carrying out the scheduling for E-DCH in a base station is disclosed by JP,2004-215276,A (patent reference 1).
Furthermore, TS25.309v6.1.0 (nonpatent reference 3) is provided as the technical specification (Technical Specification) of 3GPP which is created for E-DCH.
In release 6, E-DPDCH (Enhanced-DPDCH) and E-DPCCH (Enhanced-DPCCH) are added as uplink physical channels for E-DCH. E-DPDCH and E-DPCCH are the physical channels to which correspond to the DPDCH and DPCCH which comply with release 5 and earlier standards, the E-DPDCH is a channel via which data from the MAC layer are transmitted, and the E-DPCCH is a channel via which control information is transmitted. Furthermore, as in the case of TFC for DPDCH, it is determined that E-TFC (Enhanced-TFC) which defines the transmission rate is used. When the transmission rate is decided, a gain factor (βeu) for E-DPDCH is decided. In addition, in release 6, as downlink physical channels for E-DCH, an E-AGCH (Enhanced-Absolute Grant CHannel) and an E-RGCH (Enhanced-Relative Grant CHannel) via which scheduling results are notified, and an E-HICH (E-DCH HARQ Acknowledgement Indicator CHannel) via which a reception judgment result (ACK/NACK) is notified are added.
It is decided that at the time of data transmission from a mobile station, E-DCH and DCH data are treated as independent data streams (Data Stream), and a higher priority is given to DCH transmission than to E-DCH transmission. Thus, because E-DCH data are a data stream which is independent of DCH data and a higher priority is given to DCH transmission than to E-DCH transmission, the mobile station ensures transmit power required for the DCH transmission, selects an E-TFC in consideration of a remaining transmit power margin, and then transmits E-DCH data. The proposal R2-042447 (nonpatent reference 4) to 3GPP defines a state transition also for E-TFC which is similar to that or TFC.
The above-mentioned nonpatent reference 4 defines a transition between two states (i.e., an available state and a restricted state) as a state transition of E-TFC. In the nonpatent reference, a state transition which is made according to a scheduling result (Scheduling grants) from a fixed station is disclosed.
Hereafter, a problem with uplink transmission control which arises due to the addition of the E-DCH will be explained. As disclosed in the above-mentioned nonpatent reference 4, a case in which a state transition is defined for E-TFC will be considered. The DPCCH has a fixed transmission rate, and ensures required quality (what is called Eb/No) through transmit power control (what is called closed loop control) for maintaining the physical radio links. Because the same Eb/No needs to be ensured for other channels, a gain factor (in the case of TS25.309, referred to as a reference power offset) for deciding a power offset amount for DPCCH according to the transmission rate (E-TFC) which is used at the time of data transmission is decided.
On the other hand, in accordance with nonpatent reference 3 (see Chapters 7.1 and 7.2 of TS25.309), plural data (or two or more kinds of data) from higher-level protocol layers are multiplexed, and can be transmit via one E-DCH or E-DPDCH. A required communication quality (QoS: Quality of Service) request is made for each of upper layer data streams (referred to as a MAC-D flow according to TS25.309) which are multiplexed into an E-DCH (or an E-DPDCH in the physical layer) data stream. When actually transmitting data via the E-DPDCH according to this QoS request (information which defines this QoS request is called an HARQ profile), giving an additional power offset is defined separately. That is, in the case of E-DPDCH, when multiplexing two or more MAC-d flow data into one transmission interval (=1 TTI), a transmit power offset which is a maximum of the transmit power offsets of the two or more MAC-d flows is used on the basis of the HARQ profile of each MAC-d flow. Therefore, two or more E-DPDCH channel transmit power possible values (or equivalent channel amplitude coefficients) are equivalently set up for transmission with a certain transmission rate (E-TFC) setting.
Hereafter, control of maximum total transmit power (referred to as Pmax from here on) by a mobile station will be considered. Furthermore, assume a status in which the total transmit power of a mobile station reaches the maximum total transmit power (Pmax) when transmitting E-DCH (E-DPDCH) data. As previously explained, when two or more kinds of data from a higher-level protocol layer are multiplexed and transmitted using the E-DPDCH, a power offset amount applied to the E-DPDCH varies according to how to multiplex the data to be transmitted (i.e., the MAC-D flows). As a result, even if they are transmitted at the same transmission rate (E-TFC), it is evaluated that the total transmit power with different E-DPDCH channel transmit power reaches Pmax. A problem is therefore that because only the transmission rate is defined for the E-TFC, the state transition of the E-TFC changes with QoS for the descriptions of the data to be transmitted, and therefore the mobile station operation is not decided uniquely.
According to TS25.309, it is decided that a higher priority is be given to transmission of DCH data that to transmission of E-DCH data. The state transition of TFC is changed by evaluating whether the total transmit power of the mobile station reaches Pmax. For this reason, also when the total transmit power of the mobile station reaches Pmax because it includes the transmit power of E-DCH data transmitted in parallel to the DCH data (namely, when the total transmit power of the mobile station does not reach Pmax if no E-DCH data are transmitted), the evaluation of the state transition of TFC is affected. For this reason, when the state in which the total transmit power of the mobile station reaches Pmax continues because of successive transmission of E-DCH data, for example, the mobile station makes a transition from a “supported state” (Support) to an “excess of transmit power” (Excess Power), and then to a “blocked state” (blocked), thereby reducing the transmission rate (TFC) of DCH. In such a case, the rule to give a higher priority to DCH transmission than to E-DCH transmission loses effect as a matter of fact.
Furthermore, according to TS25.309, the transmission rate (E-TFC) at the time of E-DCH transmission is determined on the basis of margin power (i.e., a transmit power margin) in which power required for DCH transmission has been ensured from the maximum total transmit power of the mobile station. On the other hand, according to release 5, changing the Pmax specification according to whether or not transmission of HS-DPCCH data from the mobile station is carried out is defined by the technical specification TS25.101 (see Chapter 6.2.2 UE maximum output power with HS-DPCCH of nonpatent reference 5).
When E-DCH data are transmitted, the transmission rate (E-TFC) is determined from the transmit power margin. A problem is however that because the definitions of the transmit power margin are indefinite, the operation of the communications system becomes unstable and the radio resources cannot be used efficiently. It is considered that the definitions of the transmit power margin: (1) the range of the transmit power margin; (2) whether there is a necessity to change the predetermined value Pmax with a combination of channels; (3) the definitions of the transmit power margin in a case in which the total transmit power of the mobile station does not reach Pmax; and (4) the timing which defines the transmit power margin are indefinite.
In above-mentioned nonpatent reference 4 (R2-042447), a transition among the states of E-TFC is made on the basis of scheduling result information. However, the transmit power margin of the mobile station is not taken into consideration in the evaluation of the state transition of E-TFC. Therefore, the estimated transmit power which is estimated before actual transmission may exceed Pmax, depending on the selected E-TFC. When it is expected that the estimated transmit power exceeds Pmax, a process of equally scaling the powers of all the channels is carried out in order to reduce the transmit power to Pmax or lower. However, carrying out such a process may degrade the communication quality.
The present invention is made to solve the problems which arise due to the addition of the E-DCH, and it is therefore an object to provide a communication method, a mobile station, and a communication system which carry out uplink transmission control and radio resource control appropriately.